It is well known in the art to use thermoplastic materials to manufacture containers for liquids. Some of the liquids to be contained by such containers, for instance bleach-containing compositions, create internal pressure which builds up with time. In such cases, the containers are progressively subjected to deformation due to the internal pressure build-up, especially at their base. This phenomenon is often referred to as "bulging". This phenomenon is especially acute in warm countries where the containers may be exposed to particularly elevated temperatures. In some instances, bulging can be so severe so as to induce a base deformation which is such that the container can no longer stay in upright position. For instance in supermarkets, the containers may fall of the shelves.
Anti-bulging containers have been disclosed in the art, for instance in DE 16 07 895, DE 21 11 534, EP 0 002 082 and our co-pending European Application EP 91202524. These references disclose containers having a central dome, where the dome is connected to the side walls of the container by pieces of thermoplastic material of various shapes. It is therefore an object of the present invention to provide a container of thermoplastic material for containing liquids with improved resistance to bulging.
It is also an object of the present invention to provide a solution to bulging which is particularly applicable to containers of smaller size.
The problem of bulging can to some extent be addressed by increasing the quantity of thermoplastic material used, so as to manufacture a container with thick walls. However, this solution is quite objectionable from an environmental point of view as well as from an ease of manufacturing viewpoint. It is therefore an another object of the present invention to provide an anti-bulging container of thermoplastic material having walls of minimum thickness.